1. Field
This invention relates generally to a plasma power limiter and, more particularly, to a plasma power limiter that is monolithically fabricated using wafer-level processing so as to be integrated on the same wafer as other circuits.
2. Discussion of the Art
It is known in the art to provide wafer-level packaging for integrated circuits, such as monolithic millimeter-wave integrated circuits (MMIC), formed on substrate wafers. In one wafer-level packaging design, a cover wafer is mounted to the substrate wafer using a bonding ring so as to provide a hermetically sealed cavity in which the integrated circuit is provided. Typically, many integrated circuits are formed on the substrate wafer and covered by a single cover wafer, where each integrated circuit is surrounded by a separate bonding ring. The cover wafer and the substrate are then diced between the bonding rings to separate the packages for each separate integrated circuit. The dicing process typically requires the use of a saw that cuts the cover wafer between the packages, where a portion of the cover wafer is removed. The substrate wafer is then cut between the packages.
Integrated circuits can be susceptible to high intensity or high power signals, such as electromagnetic pulses (EMP), whether they be unintended random signals or intentional hostile signals. For example, high performance electronic circuits used in many receivers may be sensitive to high power input signals. Particularly, low noise amplifiers (LNA) provided immediately behind the antenna at the front end of a receiver can be destroyed if the antenna receives a high intensity power signal, where the power susceptibility of the LNA becomes more sensitive to incoming power as the frequency and noise performance of the receiver increases.
In order to address this concern related to the damaging effects of high power signals, plasma power limiters have been developed in the art that are provided at the front end of these types of circuits. A typical plasma power limiter will include a sealed cavity in which is encapsulated a suitable ionizable gas, such as argon, that when ionized becomes a plasma and allows electrical current to propagate therethrough. If the incoming signal is of a high enough intensity where the gas is ionized, current generated by the signal can be directed through the plasma to a sinking electrode, where it can harmlessly be sent to a ground potential.
Known plasma power limiters are typically separate bulky devices provided at the front end of the receiver or other circuit that cause significant signal loss before the signal can be amplified for further processing. Therefore, for some applications the design of the specific circuit would not allow for such a power limiter to be incorporated.